This should fix an error when the user has turn on AWS logging while
and upload a file with non-English filename, as `aws-sdk` logger is not
encoding aware.

The problem was that the string returned from another logger methods
is in `US-ASCII`, while the string returned from Paperclip would be in
`UTF-8`. When the logger calls `#join` on those strings, Ruby would
raise an exception.

This solution is not the best, as it involves a monkey-patching, but
should make sure that the upload goes through without any hiccup. For
the long run, I'm going to send a patch to `aws-sdk` and also make
Paperclip require at least `aws-sdk > 1.4.1`

This will prevent a pitfall as sometime the style's name can be a string.

Fixes #762

Fixes #843

ContentTypeValidator now honors the `:allow_nil` and `:allow_blank` option.

This will ensure that the content type is a String.

Fixes #805

AttachmentAdapter now handles this for us.

* Add failing test for case when no logger is specified
* add fix for failing test
* fix teardown of no logger test

In Rails, `ActionDispatch::Http::UploadedFile` has an accessor to access
a `Tempfile` object. However, `Rack::Test::UploadedFile` does not
provide that, but provinding the `#path` method instead. To be able to
support both, we have to check for existance for `#tempfile` method,
then fallback to `#path` method.

Fixes #807

It's not working correctly as expected, so let's revert this for now.

This reverts commit 51bb0f9f.

Fixes #768

Fixes #786

Needs work for S3 Attachments.

Current validation check in AttachmentContentTypeValidator is simply wrong, it will add an error if any of the allowed_types fails comparison with value, so it will pass only if value is either empty or equals to each and every one of allowed_types.

Add test to check that validation passes if even one of content types match.